1. Field of the Invention
This invention relates to a floppy disk drive, and more particularly, to a spring member attached to a turntable for rotating a floppy disk.
2. Description of the Prior Art
One of the most important things to be done for a floppy disk drive is to improve it so that it may enable a high accuracy of data recording or reproduction in or from a floppy disk. The known floppy disk drives are mainly of the direct drive type in which a turntable is connected to the output shaft of a disk drive motor for driving a floppy disk directly without employing any belt or other power transmission mechanism.
A typical device of the direct drive type is shown in FIGS. 5 to 7. It comprises a disk drive motor 1 having an output shaft 2, a turntable 3 attached to the free end of the output shaft 2, and a pulse generator 4 for detecting the phase of the turntable 3.
The motor 1 comprises a rotor 5 and a stator 6. The output shaft 2 is secured to the center of the rotor 5 and rotatably supported by bearings 7 in the stator 6 to thereby connect the rotor 5 to the stator 6. The rotor 5 comprises a circular dish-shaped rotor yoke 8 formed from a soft magnetic material, and an annular rotor magnet 9 secured to the inside of the yoke 8 and having a plurality of circumferentially equally spaced apart magnetized portions. The stator 6 comprises a stator yoke 10 formed from a soft magnetic material, and a plurality of drive coils 11 disposed in a circular array on the yoke 10 and facing the rotor magnet 9. If an electric current is supplied to the drive coils 11, the field magnetic flux created between the rotor magnet 9 and the stator yoke 10 produces torque to cause the rotor 5 to rotate relative to the stator 6.
The turntable 3 has a central hole 12 in which the output shaft 2 of the motor 1 is received, a hole 13 in which a drive pin 19 is received, and eyelets 14 in which pins 18 are received for securing a spring member 17 to the lower side of the turntable 3, as shown in FIG. 6. The turntable 3 also includes a wear-resistant plastic sheet 15 bonded to the center of its upper side around its central hole 12, and a sheet of a magnet 16, such as of rubber, bonded to its upper side outside the area in which the central hole 12, drive pin receiving hole 13 and plastic sheet 15 are provided. The drive pin 19 is secured to the spring member 17, extends through the hole 13 and has a free end 19a projecting above the turntable 3.
The spring member 17 is shown in detail in FIG. 7. It comprises a generally circular sheet of a highly elastic material, such as phosphor bronze. It has a central hole 17a in which a projection provided in the center of the lower side of the turntable 3, but not shown can be tightly fitted to position the spring member 17 relative to the turntable 3. The spring member 17 also has near its outer periphery a plurality of eyelets 17b through which the pins 18 are passed to secure it to the turntable 3. It also has an arcuate slot 17c formed on the diametrically opposite side of the central hole 17a from the eyelets 17b. The slot 17c defines a generally arcuate spring portion 17d having a radially inwardly projecting middle portion 17e to which the drive pin 19 is attached.
The pulse generator 4 comprises a magnet 20 secured to the outer surface of the rotor yoke 8 and a pickup 21 attached to the stator yoke 10 and facing the magnet 20. The pickup 21 detects the magnetic field of the magnet 20 during each rotation of the rotor yoke 8 and thereby the phase of the drive pin 19 having a specific positional relation to the magnet 20.
FIG. 8 shows by way of example a floppy disk which can be rotated by the floppy disk drive hereinabove described. The floppy disk 22 comprises a magnetic disk 23 and a disk cartridge 24 in which the disk 23 is rotatably held. The magnetic disk 23 has at its center a hub 25 formed from a metal sheet. The hub 25 has a central hole 26 in which the upper end 2a of the output shaft 2 projecting above the turntable 3 can be fitted, and a rectangular hole 27 provided radially outwardly of the central hole 26 for receiving the drive pin 19.
If the floppy disk is placed on the turntable 3, the hub 25 is attracted by the magnet sheet 16, and the upper end 2a of the output shaft 2 is passed through the central hole 26. The drive pin 19 is pressed down by the hub 25 into the hole 13 of the turntable 3 against the force of the spring member 17, as shown in FIG. 9(a). If the turntable 3 is rotated in the direction of an arrow A until the drive pin 19 is aligned with the hole 27, the drive pin 19 is urged upward into the hole 27 by the spring member 17, as shown in FIG. 9(b). If the turntable 3 is further rotated, the drive pin 19 abuts on the radially outward edge 27a of the hole 27 and the spring member 17 urges the hub 25, hence the disk 23, in the direction of an arrow B radially outwardly of the output shaft 2, as shown in FIG. 9(c). If the turntable 3 is further rotated, the drive pin 19 abuts on the front edge 27b of the hole 27 to complete the radial and circumferential positioning of the disk 23, as shown in FIG. 9(d).
As the disk 23 is positioned radially relative to the output shaft 2 by the engagement of the drive pin 19 with the outer edge 27a of the hole 27, the disk 23 can always be positioned on a fixed center of rotation and thereby enables its tracking by a recording and playback head not shown. As the disk 22 is positioned circumferentially relative to the drive pin 19 by its engagement with the front edge 27b of the hole 27, and as the circumferential phase of the drive pin 19 is detected by the pulse generator 4, the disk always has a fixed position in which it starts storing or reproducing data.
There is a floppy disk drive of the type generally as hereinabove described, and further featured by the disk drive motor 1 which stops rotation automatically to achieve savings in power consumption when no storing or reproduction of data is done for a certain period of time, while power supply is on. It is often the case with a floppy disk drive of such type that the floppy disk 22 is removed from the turntable 3 when the motor 1 has stopped, and is placed thereon again when the storing or reproduction of data is started again.
This mode of use is, however, likely to present a problem, as will hereinafter be pointed out. If the floppy disk 22 is removed from the turntable 3, the drive pin 19 is disengaged from the outer edge 27a of the hole 27 and urged radially outwardly of the hub 25 by the spring member 17. When the floppy disk 22 is placed on the turntable 3 again, therefore, the drive pin 19 is not in alignment with the hole 27 radially of the hub 25, as shown in FIG. 10(a). As the drive pin 19 has an outer portion 19a located radially outwardly of the outer edge 27a of the hole 27, it is pressed down by the hub. As it also has a front edge 19b which is substantially aligned with the front edge 27b of the hole 27, however, the drive pin 19 is not fully pressed down into the hole 13 of the turntable 3, but has an inner portion 19c projecting into the hole 27, while its front edge 19b engages the front edge 27b of the hole 27, as shown in FIG. 10(b). If the turntable 3 is rotated, therefore, the hub 25 and hence the magnetic disk 23 can be rotated, despite the failure of the drive pin 19 to fit properly in the hole 27. Although the disk 23 can be rotated, however, the recording or playback head fails to track the disk properly to enable the proper storing or reproduction of data, since the disk does not have a correctly positioned axis of rotation.